Molded fluid flow structure with saw cut channel

ABSTRACT

In an embodiment, a fluid flow structure includes a micro device embedded in a molding. A fluid feed hole is formed through the micro device, and a saw defined fluid channel is cut through the molding to fluidically couple the fluid feed hole with the channel.

BACKGROUND

A printhead die in an inkjet pen or print bar includes a plurality offluid ejection elements on a surface of a silicon substrate. Fluid flowsto the ejection elements through a fluid delivery slot formed in thesubstrate between opposing substrate surfaces. While fluid deliveryslots adequately deliver fluid to fluid ejection elements, there aresome disadvantages with such slots. From a cost perspective, forexample, ink delivery slots occupy valuable silicon real estate and addsignificant slot processing cost. In addition, lower printhead die costis achieved in part through die shrink, which is associated with tighterslot pitch and/or slot width in the silicon substrate. However,shrinking the slot pitch adds excessive assembly costs associated withintegrating a small die into the inkjet pen. Structurally, removingmaterial from the substrate to form an ink delivery slot weakens theprinthead die. Thus, when a single printhead die has multiple slots(e.g., to improve print quality and speed in a single color printheaddie, or to provide different colors in a multicolor printhead die), theprinthead die becomes increasingly fragile with the addition of eachslot.

BRIEF DESCRIPTION OF THE DRAWINGS

The present embodiments will now be described, by way of example, withreference to the accompanying drawings, in which:

FIG. 1 is an elevation section view illustrating one example of a moldedfluid flow structure implemented as a printhead structure;

FIG. 2 is a block diagram illustrating an example system implementing amolded fluid flow structure such as the printhead structure of FIG. 1;

FIG. 3 is a block diagram illustrating an inkjet printer implementingone example of a fluid flow structure in a substrate wide print bar;

FIGS. 4-6 illustrate an inkjet print bar implementing one example of amolded fluid flow structure as a printhead structure suitable for use inprinter;

FIGS. 7-9 illustrate an example process for defining a fluid channelwithin a molded body of a fluid flow structure using a rotary cuttingsaw;

FIG. 10 illustrates an example of a molded fluid flow structure prior tothe formation of a saw defined fluid channel;

FIGS. 11-15 illustrate examples of differently shaped, saw defined fluidchannels that can be cut into a molded body of a fluid flow structure;

FIG. 16 illustrates an example process for making a printhead fluid flowstructure having a saw defined fluid channel;

FIG. 17 is a flow diagram of the example process for defining a fluidchannel within a molded body of a fluid flow structure using a rotarycutting saw as illustrated in FIGS. 7-9;

FIG. 18 is a flow diagram of the example process for making a printheadfluid flow structure having a saw defined fluid channel as illustratedin FIG. 16.

Throughout the drawings, identical reference numbers designate similar,but not necessarily identical, elements.

DETAILED DESCRIPTION Overview

Reducing the cost of conventional inkjet printhead dies has beenachieved in the past through shrinking the die size and reducing wafercosts. The die size depends significantly on the pitch of fluid deliveryslots that deliver ink from a reservoir on one side of the die to fluidejection elements on another side of the die. Therefore, prior methodsused to shrink the die size have mostly involved reducing the slot pitchand size through a silicon slotting process that can include, forexample, laser machining, anisotropic wet etching, dry etching,combinations thereof, and so on. Unfortunately, the silicon slottingprocess itself adds considerable cost to the printhead die. In addition,successful reductions in slot pitch are increasingly met withdiminishing returns, as the costs associated with integrating theshrinking die (resulting from the tighter slot pitch) with an inkjet penhave become excessive.

A fluid flow structure enables the use of smaller printhead dies and asimplified method of forming fluid delivery channels to deliver ink froma reservoir on one side of a printhead die to fluid ejection elements onanother side of the die. The fluid flow structure includes one or moreprinthead dies molded into a monolithic body of plastic, epoxy moldcompound, or other moldable material. For example, a print barimplementing the new structure includes multiple printhead dies moldedinto an elongated, singular molded body. The molding enables the use ofsmaller dies by offloading the fluid delivery channels (i.e., the inkdelivery slots) from the die to the molded body of the structure. Thus,the molded body effectively grows the size of each die for makingexternal fluid connections and for attaching the dies to otherstructures. Fluid delivery channels are formed in the fluid flowstructure using a cutting saw to plunge cut through the molded body.

The described fluid flow structure is not limited to print bars or othertypes of printhead structures for inkjet printing, but may beimplemented in other devices and for other fluid flow applications.Thus, in one example, the new structure includes a micro device embeddedin a molding having a channel or other path for fluid to flow directlyinto or onto the device. The micro device, for example, could be anelectronic device, a mechanical device, or a microelectromechanicalsystem (MEMS) device. The fluid flow, for example, could be a coolingfluid flow into or onto the micro device or fluid flow into a printheaddie or other fluid dispensing micro device. These and other examplesshown in the figures and described below illustrate but do not limit theinvention, which is defined in the Claims following this Description.

As used in this document, a “micro device” means a device having one ormore exterior dimensions less than or equal to 30 mm; “thin” means athickness less than or equal to 650 μm; a “sliver” means a thin microdevice having a ratio of length to width (L/W) of at least three; a“printhead structure” and a “printhead die” mean that part of an inkjetprinter or other inkjet type dispenser that dispenses fluid from one ormore openings. A printhead structure includes one or more printheaddies. “Printhead structure” and “printhead die” are not limited toprinting with ink and other printing fluids but also include inkjet typedispensing of other fluids for uses other than or in addition toprinting.

Illustrative Embodiments

FIG. 1 is an elevation section view illustrating one example of a moldedfluid flow structure 100 implemented as a printhead structure 100 thatis suitable for use in a print bar of an inkjet printer. The printheadstructure 100 includes a micro device 102 molded into a monolithic body104 of plastic or other moldable material. A molded body 104 may also bereferred to herein as a molding 104. In general, a micro device 102could be, for example, an electronic device, a mechanical device, or amicroelectromechanical system (MEMS) device. In the present printheadstructure 100 of FIG. 1, micro device 102 is implemented as a printheaddie 102. Printhead die 102 includes a silicon die substrate 106comprising a silicon sliver on the order of 100 microns in thickness.The silicon substrate 106 includes fluid feed holes 108 dry etched orotherwise formed therein to enable fluid flow through the substrate 106from a first exterior surface 110 to a second exterior surface 112. Thesilicon substrate 106 further includes a thin silicon cap 114 (i.e., acap over the silicon substrate 106) adjacent to and covering the firstexterior surface 110. The silicon cap 114 is on the order of 30 micronsin thickness and can be formed of silicon or some other suitablematerial.

Formed on the second exterior surface 112 of substrate 106 are one ormore layers 116 that define a fluidic architecture that facilitates theejection of fluid drops from the printhead structure 100. The fluidicarchitecture defined by layers 116 generally includes ejection chambers118 having corresponding orifices 120, a manifold (not shown), and otherfluidic channels and structures. The layer(s) 116 can include, forexample, a chamber layer formed on the substrate 106 with a separatelyformed orifice layer over the chamber layer, or they can include amonolithic layer that combines the chamber and orifice layers. Layer(s)116 are typically formed of an SU8 epoxy or some other polyimidematerial.

In addition to the fluidic architecture defined by layer(s) 116 onsilicon substrate 106, the printhead die 102 includes integratedcircuitry formed on the substrate 106 using thin film layers andelements not shown in FIG. 1. For example, corresponding with eachejection chamber 118 is a thermal ejector element or a piezoelectricejector element formed on substrate 106. The ejection elements areactuated to eject drops or streams of ink or other printing fluid fromchambers 118 through orifices 120.

The printhead structure 100 also includes signal traces or otherconductors 122 connected to printhead die 102 at electrical terminals124 formed on substrate 106. Conductors 122 can be formed on structure100 in various ways. For example, conductors 122 can be formed in aninsulating layer 126 as shown in FIG. 1, by a lamination or depositionprocess. Insulating layer 126 is typically a polymer material thatprovides physical support and insulation for conductors 122. In otherexamples, conductors 122 can be molded into molded body 104.

A saw defined fluid channel 128 is formed through the molded body 104and the thin silicon cap 114, and connects with the printhead diesubstrate 106 at the exterior surface 110. The fluid channel 128 opens apathway through the molded body and thin silicon cap 114 that enablesfluid to flow directly into the silicon substrate 106 through the fluidfeed holes 108, and onto the silicon substrate 106 at exterior surface110. As discussed in further detail below, the fluid channel 128 isformed through the molded body 104 using a cutting saw such as a rotarycutting saw.

FIG. 2 is a block diagram illustrating a system 200 implementing amolded fluid flow structure 100 such as the printhead structure 100shown in FIG. 1. System 200 includes a fluid source 202 operativelyconnected to a fluid mover 204 configured to move fluid to a channel 128in fluid flow structure 100, such as a saw defined fluid channel 128 ina printhead structure 100. A fluid source 202 might include, forexample, the atmosphere as a source of air to cool an electronic microdevice 102 or a printing fluid supply for a printhead die 102. Fluidmover 204 represents a pump, a fan, gravity or any other suitablemechanism for moving fluid from source 202 to flow structure 100.

FIG. 3 is a block diagram illustrating an inkjet printer 300implementing one example of a fluid flow structure 100 in a substratewide print bar 302. Printer 300 includes print bar 302 spanning thewidth of a print substrate 304, flow regulators 306 associated withprint bar 302, a substrate transport mechanism 308, ink or otherprinting fluid supplies 310, and a printer controller 312. Controller312 represents the programming, processor(s) and associated memories,and the electronic circuitry and components needed to control theoperative elements of a printer 300. Print bar 302 includes anarrangement of printhead dies 102 for dispensing printing fluid on to asheet or continuous web of paper or other print substrate 304. Eachprinthead die 102 receives printing fluid through a flow path fromsupplies 310 into and through flow regulators 306 and fluid channels 128in print bar 302.

FIGS. 4-6 illustrate an inkjet print bar 302 implementing one example ofa molded fluid flow structure 100 as a printhead structure 100 suitablefor use in printer 300 of FIG. 3. Referring to the plan view of FIG. 4,printhead dies 102 are embedded in an elongated, monolithic molding 104and arranged generally end to end in rows 400 in a staggeredconfiguration in which the printhead dies 102 in each row overlapanother printhead die in that same row. In this configuration, each row400 of printhead dies 102 receives printing fluid from a different sawdefined fluid channel 128 (illustrated with dashed lines in FIG. 4).Although four fluid channels 128 feeding four rows 400 of staggeredprinthead dies 102 is shown (e.g., for printing four different colors),other suitable configurations are possible. FIG. 5 illustrates aperspective section view of the inkjet print bar 302 taken along line5-5 in FIG. 4, and FIG. 6 illustrates a section view of the inkjet printbar 302 taken along line 5-5 in FIG. 4. The section view of FIG. 6 showsvarious details of a printhead structure 100 as discussed aboveregarding FIG. 1.

While a particular shape or configuration of a saw defined fluid channel128 has been generally illustrated and discussed with reference to FIGS.1-6, a variety of differently configured fluid channels 128 areachievable using a cutting saw. As discussed below, FIGS. 11-15illustrate examples of differently shaped, saw defined fluid channels128 that can be readily cut into a molded body 104 of a fluid flowstructure 100 using cutting saws having differently shaped peripheralsaw blade edges such as those shown in FIGS. 7-9.

FIGS. 7-9 illustrate an example process for defining a fluid channel 128within a molded body 104 of a fluid flow structure 100 using a rotarycutting saw 700. FIG. 17 is a flow diagram 1700 of the processillustrated in FIGS. 7-9. FIG. 7 shows a side elevation viewillustrating an example method of forming a saw defined fluid channel128 in a molded fluid flow structure 100. The side elevation view ofFIG. 7 is taken along line 7-7 in both FIGS. 8 and 9. FIG. 8 shows anelevation section view illustrating an example method of forming a sawdefined fluid channel 128 in a molded fluid flow structure 100 using arotary cutting saw 700 having a generally squared peripheral saw bladeedge 800. The generally squared peripheral saw blade edge 800 ischaracterized by the sides of the rotary saw 700 remaining parallel toone another all the way to the peripheral edge of the saw. FIG. 9 showsan elevation section view illustrating an example method of forming asaw defined fluid channel 128 in a molded fluid flow structure 100 usinga rotary cutting saw 700 having a generally tapered peripheral saw bladeedge 900. The generally tapered peripheral saw blade edge 900 ischaracterized by the sides of the rotary saw 700 diverging inward towardone another near the peripheral edge of the saw. The section views ofFIGS. 8 and 9 are taken along lines 8-8 and 9-9 in FIG. 7.

Referring now primarily to FIG. 700 and FIG. 17, while the molded fluidflow structure 100 is held in a fixed position, the rotary cutting saw700 is activated to rotate, for example, in a clockwise direction 702 tobegin cutting a fluid channel 128 in the structure 100 (step 1702 inFIG. 17). The peripheral cutting edge (e.g., 800, 900) of rotary cuttingsaw 700 can be jagged and/or have an abrasive material formed thereon inorder to perform the cutting operation as the saw rotates. For example,the saw 700 can have a diamond encrusted cutting edge. The rotarycutting saw 700 is lowered in a vertical direction to engage and plungecut the molded body 104 (see dashed line representation 704 of the saw700) (step 1704 in FIG. 17). In particular, the rotary cutting saw 700is moved in a first direction 706 perpendicular to the exterior surface110 of silicon substrate 106 to partially form the fluid channel 128 inthe molded body 104 and the silicon cap 114. That is, the saw 700 islowered through both the molded body 104 and the silicon cap 114 (seedashed line representation 708 of the saw 700) which partially forms thefluid channel 128. The rotary cutting saw 700 is then moved horizontallyto drag cut the molded body 104 and silicon cap 114 (see dashed linerepresentation 710 of the saw 700) (step 1706 in FIG. 17). Inparticular, the rotary cutting saw 700 is moved in a second direction712 parallel to the exterior surface 110 of silicon substrate 106 tocomplete formation of the fluid channel 128. The rotary cutting saw 700can then be moved along horizontal direction 714 and vertical direction716 back to its initial position (step 1708 in FIG. 17).

The variously shaped, saw defined fluid channels 128 shown in FIGS.11-15 are formed in the same general manner as just discussed aboveregarding FIG. 7. However, in forming different shaped channels 128,rotary saw blades having differently shaped peripheral cutting edges(e.g., FIG. 8, 800; FIG. 9, 900) can be used separately or incombination, and in varying orders of application to the molded fluidflow structure 100. Furthermore, while the fluid channels 128 are formedsuch that they run generally parallel to the length of an elongated,monolithic molded body (see FIGS. 4-6), and in correspondence with thelengths of the printhead dies 102, channels can also be saw cut indifferent orientations, such as orientations that are perpendicular tothose illustrated. Channels cut in such a manner can route fluid throughthe fluid flow structure 100 in different directions and for varyingpurposes. For example, channels cut perpendicular to those shown inFIGS. 4-6, can serve to join two parallel channels with a perpendicularchannel link.

Referring now to FIG. 10, a molded fluid flow structure 100 is shownprior to the formation of a saw defined fluid channel 128. The fluidflow structure 100 is configured in the same general manner as discussedabove with regard to FIG. 1, except that the conductors 22 are shownembedded within the molded body 104 rather than within a separateinsulating layer 126. This configuration is used throughout FIGS. 10-15for the general purpose of simplifying the illustrations.

Referring now to FIG. 11, a saw defined fluid channel 128 has beenformed with first and second side walls, S₁ and S₂, that aresubstantially parallel to one another. The parallel side walls S₁ andS₂, can be formed, for example, using a rotary cutting saw 700 as shownin FIG. 8. The rotary cutting saw 700 of FIG. 8 has a generally squaredperipheral saw blade edge 800 characterized by parallel blade sides,which when plunged into the molded body 104 of fluid flow structure 100removes molding material and silicon from the thin silicon cap 114,leaving substantially parallel saw cut side walls, S₁ and S₂.

FIG. 12 illustrates a saw defined fluid channel 128 formed with firstand second side walls, S₁ and S₂, that are tapered with respect to oneanother. The tapered side walls taper toward one another as they getcloser to the fluid feed holes 108 in substrate 106, and away from oneanother as they recede from substrate 106. The tapered side walls S₁ andS₂, can be formed, for example, using a rotary cutting saw 700 as shownin FIG. 9. The rotary cutting saw 700 of FIG. 9 has a generally taperedperipheral saw blade edge 900 characterized by the sides of the rotarysaw 700 diverging inward toward one another near the peripheral edge ofthe saw. When plunged into the molded body 104 of fluid flow structure100 the saw with saw blade edge 900 removes molding material and siliconfrom the thin silicon cap 114, leaving tapered, saw cut side walls, S₁and S₂.

FIGS. 13, 14, and 15, each illustrates a saw defined fluid channel 128formed with first and second side walls, S₁ and S₂, that are bothsubstantially parallel and tapered with respect to one another. Theparallel sections of side walls S₁ and S₂, can be formed using a rotarycutting saw 700 as shown in FIG. 8, and the tapered sections of sidewalls S₁ and S₂, can be formed using a rotary cutting saw 700 as shownin FIG. 9. Sidewall sections having different tapering angles are formedusing cutting saws 700 as shown in FIG. 9 whose sides have varyingangles of divergence inward toward one another as they near theperipheral edge of the saw.

In FIG. 13, the parallel sections of side walls S₁ and S₂ are adjacentto the sliver substrate 106, and the tapered sections taper inwardtoward one another to meet the parallel sections. In FIG. 14, thetapered sections of side walls S₁ and S₂ are adjacent to the sliversubstrate 106. The tapered sections taper toward one another to meet thesliver substrate 106 and taper away from one another to meet theparallel side wall sections. In FIG. 15, parallel sections of side wallsS₁ and S₂ are adjacent to the sliver substrate 106, and a first set oftapered sections taper inward toward one another to meet the parallelsections. A second set of tapered sections taper inward to meet thefirst set of tapered sections.

In general, the saw cut fluid channels 128 shown in FIGS. 11-15 havechannel side walls, S₁ and S₂, formed in various parallel and or taperedconfigurations. Channel side walls that diverge or taper away from oneanother as they recede from the printhead sliver substrate 106 providethe benefit of helping air bubbles move away from the orifices 120,ejection chambers 118, and fluid feed holes 108, where they mayotherwise hinder or prevent the flow of fluid. Accordingly, the fluidchannels 128 shown in FIGS. 11-15 comprise side walls that are paralleland/or divergent as they recede from the sliver substrate 106. However,the illustrated channel side wall configurations are not intended to bea limitation as to other shapes and configurations of side walls withinsaw defined fluid channels 128. Rather, this disclosure contemplatesthat other saw defined fluid channels are possible that have side wallsshaped in various other configurations not specifically illustrated ordiscussed.

FIG. 16 illustrates an example process for making a printhead fluid flowstructure 100 having a saw defined fluid channel 128. FIG. 18 is a flowdiagram 1800 of the process illustrated in FIG. 16. As shown in FIG. 16at part “A”, a printhead die 102 is attached to a carrier 160 using athermal release tape 162 (step 1802 in FIG. 18). The printhead die 102is placed with the orifice side down onto the carrier 160. The printheaddie 102 is in a pre-processed state such that it already includeslayer(s) 116 defining fluidic architectures (e.g., ejection chambers118, orifices 120), and electrical terminals 124 and ejection elements(not shown) formed on sliver substrate 106. Fluid feed holes 108 havealso already been dry etched or otherwise formed in sliver substrate106.

As shown at part “B” of FIG. 16, the printhead die 102 is molded into amolded body 104 (step 1804 in FIG. 18). In one example, the die 102 iscompression molded using a mold top 164. As shown at part “C” of FIG.16, the carrier 160 is released from the thermal tape 162 and the tapeis removed (step 1806 in FIG. 18). At part “D” of FIG. 16, a polymerinsulating layer 126 is laminate onto the orifice side of the printheaddie 102, and then patterned and cured (step 1808 in FIG. 18). An SU8firing chamber protection layer 166 is deposited over the fluidicarchitecture layer(s) 116, as shown in FIG. 16 at part “E” (step 1810 inFIG. 18). At part “F” as shown in FIG. 16, a metal layer (Cu/Au) isdeposited onto the polymer insulating layer 126 and patterned intoconductor traces 122 (step 1812 in FIG. 18). A top polymer insulatinglayer 126 is then spin coated over the conductor traces 122, and thenpatterned and cured as shown at part “G” of FIG. 16 (step 1814 in FIG.18). At part “H” of FIG. 16, the firing chamber protect layer 166 isstripped off and a final cure of the polymer insulating layer 126 isperformed (step 1816 in FIG. 18). As shown at part “I” of FIG. 16, a sawcut fluid channel 128 is then formed into the backside of the printheadfluid flow structure 100. The fluid channel 128 is formed as describedabove regarding the fluid channel forming process shown in FIGS. 7 and17. The fluid channel 128 can be configured in various shapes such asthose discussed above with reference to FIGS. 11-15.

What is claimed is:
 1. A fluid flow structure, comprising: a microdevice embedded in a molding; a fluid feed hole formed through the microdevice; and a saw defined fluid channel cut through the molding thatfluidically couples the fluid feed hole with the channel.
 2. A structureas in claim 1, wherein the channel comprises first and secondsubstantially parallel side walls.
 3. A structure as in claim 1, whereinthe channel comprises first and second tapered side walls.
 4. Astructure as in claim 3, wherein the tapered side walls taper toward oneanother as they get closer to the fluid feed holes.
 5. A structure as inclaim 1, wherein the channel comprises first and second side walls thatinclude both tapered side wall sections and substantially parallel sidewall sections.
 6. A structure as in claim 5, wherein the tapered sidewall sections are adjacent the micro device such that they taper towardone another to meet the micro device and taper away from one another tomeet the parallel side wall sections.
 7. A structure as in claim 5,wherein the parallel side wall sections are adjacent the micro deviceand the tapered side wall sections taper toward one another to meet theparallel side wall sections.
 8. A structure as in claim 1, furthercomprising a silicon cap over the micro device, wherein the saw definedfluid channel comprises a saw defined fluid channel cut through both themolding and the silicon cap to fluidically couple the fluid feed holewith the channel.
 9. A structure as in claim 1, wherein the side wallsare molded side walls.
 10. A method of making a fluid channel in aprinthead fluid flow structure, comprising: activating a rotary cuttingsaw; and plunge cutting the saw into a molded body of the printheadfluid flow structure to form a fluid channel.
 11. A method as in claim10, wherein plunge cutting the saw comprises plunge cutting the sawthrough the molded body and through a silicon cap that covers fluid feedholes in a sliver silicon substrate.
 12. A method of making a printheadstructure, comprising: molding a printhead die within a molded body; andsawing a fluid channel into the molded body with a cutting saw.
 13. Amethod as in claim 12, wherein sawing a fluid channel comprises sawing afluid channel through the molded body and through a silicon cap thatcovers fluid feed holes in a sliver silicon substrate of the printheaddie.
 14. A method as in claim 13, wherein sawing through the silicon capfluidically couples the fluid channel to the feed holes, enabling fluidflow from the fluid channel through the sliver silicon substrate.
 15. Amethod as in claim 13, wherein sawing a fluid channel comprises sawing afluid channel having side walls that taper toward one another as theyget closer to the sliver silicon substrate.